Project Objectives: Molecular Diagnostic Systems Following initial virulent infection and immune response, Epstein- Barr virus (EBV) is retained for the life of the individual in a latent state. EBV may become reactivated during subsequent immunodeficient or immunosuppressive states. EBNA-1 and EA-D are two EBV polypeptides which are indicators of latent and virulent states of the virus, respectively. The Phase I studies will concentrate on these two antigens. Molecular Diagnostic Systems, Inc. has already developed monoclonal antibodies to EBNA-1 and EA- D, characterized these for specificity, and demonstrated that these antibodies recognize the appropriate EBV antigens in cells containing EBV. The goal of Phase I studies is to evaluate further these monoclonal antibodies as reagents by: defining the epitopes recognized by these monoclonal antibodies and developing purification methods for EA-D and EBNA-1 using these monoclonal antibodies. Following further development during Phase II, these monoclonal antibodies may be used clinically to identify antigens in pathological samples and potentially as capture antibodies for diagnostic screening.